Get to know your amazing body and the science behind how periods work.
Your period (or "menstruation") is the monthly shedding of blood and tissue from your uterus through the opening of your vagina. Menstruation is an important part of the reproductive process and is a signal that you're maturing and that you're healthy.
To understand your period, it's a good idea to get to know the parts of the female reproductive system. Here's what you look like on the inside:
And here's what's going on the outside:
When you hit puberty, your hormones are sending all kinds of signals to areas inside your body to start growing and maturing. Estrogen and progesterone are the major hormones controlling your reproductive system and your menstrual cycle. Your cycle is made up of three distinct phases: menstruation, the follicular phase and the luteal phase.
Just before your first period, these hormones will signal your ovaries to get ready to release an egg. At the same time, the lining of your uterus (endometrium) will start to thicken.
After the ovary releases the egg, it travels down the fallopian tube to the uterus. The time it takes for your body to do this can vary from woman to woman, and this is why some women have longer cycles than others.
This is the time when many women experience PMS (or Premenstrual Syndrome). You might feel bloated or achy, with sore breasts and cramps in your pelvis or back from PMS. You might also have less energy or experience headaches, diarrhea or constipation, nausea, dizziness or fainting.
The transition between the follicular and the luteal phase is called ovulation, when a woman is at her most fertile. If the egg is fertilized (by sperm), then attaches to the lining of the uterus, pregnancy begins.
If the egg is not fertilized or doesn't implant, the lining of the uterus starts to break down, causing bleeding. This is the beginning of your "period" and Day 1 of your cycle. Bleeding may last anywhere from 4-7 days, with the most blood loss occurring in the first 3 days.
The entire cycle repeats every 28 days or so, but it's different for everyone. It's common for young women to have irregular cycles for the first couple of years after they get their period. As you get older, your period should become more regular. Keeping track of when your period stops and starts will help you better understand your cycle.
Now that you know a little bit more about your amazing body, you can impress your biology teacher - and your girlfriends - with your new vocabulary.
Learn about the key hormone changes that make up your menstrual cycle and the physical and emotional changes that those hormones create.
Learn MoreLearn the signs your body is giving you so you know when an irregular period is more than the body making a normal adjustment.
Learn MoreNo two periods are the same. Learn how they can vary from woman to woman.
Learn MoreThis is not intended to be medical advice. Everybody is different so please make sure to consult your physician if you're having issues. Do not delay or refrain from seeking professional medical advice from your physician because of something you have read on this site.
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Tracking is simple! Use our FREE Period Calculator to figure out when your next period starts.